The present disclosure relates to an image forming apparatus equipped with an exposure device.
Conventionally, there is known an image forming apparatus, which forms an electrostatic latent image on a photoreceptor drum and develops the electrostatic latent image formed on the photoreceptor drum so as to obtain a toner image. This image forming apparatus includes an exposure device for emitting a light beam for scanning and exposing the photoreceptor drum.
The exposure device includes an exposure member constituted of a semiconductor laser element, a polygon mirror and the like, and has a structure in which the exposure member is housed in a casing. The casing is provided with an opening for emitting the exposing light beam, and the opening is closed by a transparent plate such as a glass plate for preventing toner and the like from entering into the device through the opening. In other words, the exposing light beam is emitted through the transparent plate. In this case, if toner and the like adhere to the transparent plate and contaminate the same, intensity of the exposing light beam is decreased, or the exposing light beam is scattered, so that quality of a printed image is deteriorated. Therefore, a cleaning mechanism is necessary for cleaning the transparent plate.
Conventionally, for example, a cleaning mechanism is provided, in which a cleaner is disposed so as to contact with the transparent plate, and the cleaner is moved in a main scanning direction so that the transparent plate is cleaned. This cleaning mechanism includes, in addition to the cleaner, a ball screw extending in the main scanning direction, a motor connected to the ball screw, and the like. Further, the cleaner is engaged with the ball screw. In this way, when the ball screw is driven to rotate, the cleaner is moved in the main scanning direction while contacting with the transparent plate, and hence the transparent plate is cleaned.
Conventionally, when the cleaning operation is not performed, the cleaner stands by outside a scanning range of the exposing light beam (at an initial position). When the cleaning operation is performed, the cleaner moves in the main scanning direction so as to clean the transparent plate. After that, the cleaner returns to the initial position. In this way, when the exposure device performs exposure, the exposing light beam is not blocked by the cleaner.
However, when the cleaning operation is being performed, if the cleaner is caught by a certain member or if a foreign object is pinched between the cleaner and the ball screw, the cleaner may not return to the initial position (the cleaner stays in the scanning range of the exposing light beam). In other words, an error occurs in the cleaning operation. Then, if the printing job (including exposure by the exposure device) is performed in a state where the cleaner has not returned to the initial position, the exposing light beam is blocked by the cleaner. Therefore, a position on the photoreceptor drum corresponding to the position where the cleaner stays is not exposed, and hence quality of the printed image is deteriorated.
In order to solve this inconvenience, an additional mechanism should be provided for determining whether or not the cleaner has returned to the initial position and to inhibit execution of the printing job until the cleaner returns to the initial position. For instance, if a detection sensor for detecting arrival of the cleaner is disposed at the initial position, it is possible to determine whether or not the cleaner has returned to the initial position on the basis of an output of the detection sensor. However, in this case, the detection sensor for detecting arrival of the cleaner is necessary, and hence the number of components is increased resulting in cost increase.